Drafting spline



April 30, 1957 R. WILKES DRAFTING SPLINE Filed Jan. 5, 1956 11v REUBENILKES b/QM United States Patent ice 2,790,245 DRAFTING SPLlNE ReubenWilkes, Seattle, Wash. Application January 3, 1956, Serial No. 556,934

2 Claims. (Cl. 33-177) This invention relates to drafting splines to beused by draftsmen in the ruling of irregularly curved lines, forexample, in the ruling of railway curves, ships lines and other curvedlines; it being the principal object of the invention to provide aspline that is exceptionally flexible; that can be easily held in placeupon the drafting surface; which is of such resiliency that it can beeasily flexed to the desired curvature and which will immediately assumea normal straight condition when released from any curved formation.

It is a further object of the present invention to provide a spline ofthe above stated kind wherein a thin, flexible, flat strip of resilientmaterial forms a ruling member and to which strip a relatively thickbacking strip of sponge rubber is attached; this latter strip providinga member that is adapted to rest upon the drafting surface to hold theruling strip on edge and against which slight downward pressure may beapplied to cause it to frictionally adhere to the surface and thus tohold the ruling strip in any curved formation to which it has been bent.

It is a further object of the invention to give the foam rubber backingstrip such cross-sectional form that when the spline is bent to a sharpcurve it will not form a bulge at the bend that will cause the metalstrip to be tilted to a degree that would make its use for rulingdifiicult.

Further objects of the invention reside in the details of constructionof parts and in their combination and use, as will hereinafter be fullydescribed.

In accomplishing the above mentioned and other objects of the presentinvention, I have provided the improved details of construction, thepreferred forms of which are illustrated in the accompanying drawings,wherein:

Fig. l is a perspective view illustrating the present spline in use;showing one way of holding it in place while a line is being ruled.

Fig. 2 is a top view of the spline in its normal straight form as laidupon a drafting surface and illustrating in broken lines, the manner inwhich it can be flexed for the ruling of various irregular curves.

Fig. 3 is a cross-sectional view of the spline, particularlyillustrating the beveling of its under surface relative to the plane ofthe metal strip.

Fig. 4 is a perspective view illustratingthe use of weights or ducks forholding a position of the spline on a drafting surface.

Referring more in detail to the drawings:

The present spline comprises a single straight strip of thin, flexibleresilient material such as, for example, a strip of spring steel. Thelength of the strip is optional, but I have found that a practicallength for such devices, as provided for use by mechanical draftsmen, isfrom ten to twenty inches. For ruling ships curves or railway curves, itmay be made in greater lengths. The width of the metal strip 10 may bevaried but it has been found most practical, especially if the spline isshort, to keep 2,790,245 Patented Apr. 30, 1957 inch. The strip ofspring steel is of such resiliencythat,

-if -'bent -from its normally straight form and then resleasedfi itwill-instantly spring back to a normally straight condition.

A: sponge rubbens'trip 1 2 is vuleanized,- glued or otherwise fixed towhat will be referred to as the back side of the metal strip 10. Thisstrip 12 being coextensive with the metal strip 10 and of the sameheight. Its thickness is approximately equal to the vertical width orheight of the metal strip towhich it is applied so that in crosssectionit is substantially square, except for a slight beveling of its lowersurface as shown in Fig. 3, the purpose of which will now be explained.

It will be observed by reference to Fig. 3, that the top surface of thesponge rubber strip 12 is flush with the top edge of the metal strip 10and at a right angle to the vertical plane of the metal strip. Also, itwill be observed that the under surface of the rubber strip 12 isbeveled at an angle of approximately 5 relative to the horizontal planeof the surface on which the spline rests. In view of the fact that therubber strip, when bent sharply for the ruling of an outside curve, willbe compressed at the bend, and a downward bulge will be formed inaccordance with the extent of the bending, this downward bulging withoutthe beveling of the rubber strip, would cause the ruling strip 10 of thespline to be tilted forwardly, thus making its use for ruling difllcult.The bending of the spline to any curved form, for example, to thereverse curve as shown in Fig. 4, will cause the metal strip to be heldin a vertical position on the drafting surface regardless of thebeveling of its under surface. It is only when it is perfectly straightthat it will rest on its beveled surface.

In Fig. I, I have shown the usual way in which a draftsman holds thespline on a drafting surface with one hand while ruling a line with theother, using the metal strip 10 as the ruling guide. In Fig. 4, I haveshown the spline as held in place by ducks 15, these being lead weightsadapted to rest on the drafting surface, and which have fingers 15fextending therefrom, formed with downturned points 15p at their, outerends adapted to be holdingly engaged with the top surface of the rubberstrip 15 to hold the spline in a set position.

It is not my intention that the spline shall be restricted as tomaterials used in its making, or to its length or cross-sectionaldimensions. A plastic strip might be used in lieu of the spring steelstrip 10 described, and the two strips might be adhesively or otherwisejoined. Furthermore, while it is desirable and advantageous to bevel theunder surface of the rubber strip, the device can be used with a certaindegree of success without such beveling and therefore it is not desiredto confine the invention to the beveled strip.

Such splines are easy to use, practical and relatively inexpensive.

Having thus described my invention, what I claim as new therein anddesire to secure by Letters Patent is:

1. A drafting spline comprising a thin, flexible and resilient strip ofmetal, or the like, of uniform dimensions throughout its full length,serving as a ruling edge, and a resilient relatively thick strip. ofsponge rubber fixed'to said metal strip along the back face thereof andextending to its full length; said sponge rubber strip, having uniformcross-sectional dimensions throughout its length andhaving a top surfacethat is flush with the top surface of the metal strip and at a rightangle thereto, and having a fiat bottom surface that is flush with thebottom surface of the metal strip and adapted to be pressed intofrictional holding contact with the surface the under surface thereof isbeveled at a slight angle.up- 10 wardly and rearwardly from the loweredge of the metal strip. 7 7

References Cited in the file of this patent UNITED STATES PATENTS FisherApr. 27, 1858 Davenport May 20, 1884 Williams July 23, 1889 Moses Apr.18, 1939 FOREIGN PATENTS Italy June 8, 1935

